Abstract

The main objective of this study was to describe the spatial distribution of Hesperodiaptomus shoshone (Forbes SA, 1893) and Leptodiaptomus coloradensis (Marsh, 1911). I then attempted to determine whether mating and reproductive potential (proportion of females carrying spermatophores, the proportion of females carrying clutches and the proportion of males attaching spermatophores) were affected by spatial distribution. The final goal was to determine whether there was a size difference between individuals inside and outside aggregations and a corresponding clutch size difference. Samples were taken from four ponds located at Mexican Cut, Colorado. Results indicated that H. shoshone had a patchy distribution while L. coloradensis showed a random pattern in its dispersion. Further analyses were only performed on H. shoshone . Mating potential was higher for both males and females within aggregations. However females within aggregations did not carry clutches more often than females outside aggregations. Females within aggregations were significantly larger, but no difference was observed among males and clutch size was significantly larger for females within aggregations. The distribution of H. shoshone may in part be attributed to physical processes and local pressures such as predation and food allocation. From an adaptive standpoint, their distribution patterns seem to increase the frequency of mating encounters, thereby enhancing the mating potential of individuals found within these patches.